全文获取类型
收费全文 | 43730篇 |
免费 | 3306篇 |
国内免费 | 13篇 |
专业分类
47049篇 |
出版年
2023年 | 283篇 |
2022年 | 490篇 |
2021年 | 920篇 |
2020年 | 683篇 |
2019年 | 855篇 |
2018年 | 1156篇 |
2017年 | 1051篇 |
2016年 | 1414篇 |
2015年 | 1858篇 |
2014年 | 2054篇 |
2013年 | 2625篇 |
2012年 | 3062篇 |
2011年 | 2872篇 |
2010年 | 1950篇 |
2009年 | 1834篇 |
2008年 | 2282篇 |
2007年 | 2222篇 |
2006年 | 1985篇 |
2005年 | 1708篇 |
2004年 | 1753篇 |
2003年 | 1520篇 |
2002年 | 1437篇 |
2001年 | 1100篇 |
2000年 | 1002篇 |
1999年 | 866篇 |
1998年 | 505篇 |
1997年 | 392篇 |
1996年 | 366篇 |
1995年 | 355篇 |
1994年 | 300篇 |
1993年 | 283篇 |
1992年 | 455篇 |
1991年 | 449篇 |
1990年 | 398篇 |
1989年 | 384篇 |
1988年 | 333篇 |
1987年 | 343篇 |
1986年 | 292篇 |
1985年 | 285篇 |
1984年 | 223篇 |
1983年 | 219篇 |
1982年 | 178篇 |
1981年 | 141篇 |
1980年 | 137篇 |
1979年 | 189篇 |
1978年 | 142篇 |
1975年 | 141篇 |
1974年 | 168篇 |
1973年 | 157篇 |
1972年 | 129篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
From the roots of Ferula loscosii the coumarins umbelliprenin, coladin and coladonin and the new natural isovaleryl derivative of the latter have been isolated. A study which confirms the structure of coladonin and its difference from farnesiferol A is also given. 相似文献
42.
Fabián Michelangeli Dalia M. Sulcas Marie-Christine Ruiz 《Cell and tissue research》1987,250(2):413-419
Summary This study is concerned with electron-microscopic observations on endocrine or paracrine cells in the fundic gastric mucosa of the bullfrog. Also, an attempt was made to identify the histamine-releasing cells involved in the secretagogue response. At least three distinct endocrine-like cell types were found. The classification is based on the appearance of secretory granules and other organelles, and the relationship of endocrine-like cells with other cells in the tissue. The amphibian endocrine-like cells resemble the ECL, D and EC cells of mammals. Type-I (ECL) cells showed degranulation after repeated stimulation with tetragastrin (TG), acetylcholine (ACh) and K+ depolarizing solution, all of which release histamine. 相似文献
43.
Production of vanillic acid from vanillin by resting cells of Serratia marcescens. 总被引:2,自引:2,他引:0 下载免费PDF全文
Resting-cell suspensions of Serratia marcescens were able to convert, quantitatively, 0.3% vanillin to vanillic acid. The vanillic acid-producing activity reached a maximum after 28 h of incubation with 0.01% vanillin as an inducer. 相似文献
44.
45.
R. Brändén T. Nilsson S. Styring 《Biochemical and biophysical research communications》1980,92(4):1297-1305
A sensitive and reliable method to determine the stereochemical composition of 3-phosphoglyceric acid is presented. Results obtained with this method show that 3-phosphoglyceric acid formed in the ribulose-1,5-bisphosphate carboxylase reaction is a mixture of 10% L-3-PGA and 90% D-3-PGA. 相似文献
46.
47.
48.
Susanne Berglund Bryan J. Egner Henrik Gradén Joakim Gradén David G.A. Morgan Tord Inghardt Fabrizio Giordanetto 《Bioorganic & medicinal chemistry letters》2009,19(15):4268-4273
Herein, we disclose the discovery and optimization of 2-piperidin-4-yl-acetamide derivatives as MCH-R1 antagonists. Structural investigation of piperidin-4-yl-amide and piperidin-4-yl-ureas identified 2-piperidin-4-yl-acetamide-based MCH-R1 antagonists with outstanding in vivo efficacy but flawed with high affinity towards the hERG potassium channel. While existing hERG SAR information was employed to discover highly potent MCH-R1 antagonists with minimized hERG inhibition, additional hurdles prevented their subsequent clinical exploration. 相似文献
49.
50.
F Rabanal I Haro F Reig J M García-Antón 《International journal of peptide and protein research》1990,36(1):26-30
The synthesis of three hepatitis B surface antigens derived from S and pre-S proteins (adw S(140-147), [Tyr148] adw S(139-148), and adw pre-S(120-145)) has been accomplished by the continuous flow Fmoc-polyamide solid phase method. The use of different scavengers and trimethylsilyl bromide (TMSBr) in trifluoroacetic acid as deprotecting procedures is discussed. 相似文献